Mechanism of sulfur transfer from 1,2,4-dithiazolidine-3,5-diones to triphenylphosphines

Abstract

The mechanism of sulfurization of substituted triphenylphosphines with 4-(3-and 4-substituted)-1,2,4dithiazolidine-3,5-diones in acetonitrile, dichloromethane, tetrahydrofuran and toluene at 25 C was studied. The reaction pathway involves rate-limiting initial nucleophilic attack of the phosphorus at sulfur followed by fast decomposition of the phosphonium intermediate to the corresponding phosphine sulfide, phenylisocyanate and carbonylsulfide. From the Hammett correlations and from the solvent dependency, it was concluded that the transition-state structure is very polar and resembles the zwitter-ionic intermediate. The extent of P-S bond formation and S-S bond cleavage is very similar in the solvents series, but the latter gradually decreases with the decreasing polarity of the solvent.

Dithiasuccinoyl-Caged Amines Enables COS/H2S Release Lacking Electrophilic Byproducts

“…We hypothesized that DTS-caging of functionalized anilines would allow COS/H 2 Sr elease rates to be tuned based on prior work aimed at solvent-dependent linear free energy relationship investigations into the phosphine-mediated sulfur extrusion from DTS. [33] Additionally,w ee xpected that the caging of alkyl amines would lead to stabilization of the COS-releasing thiocarbamic acid intermediate and subsequentlyd ecrease the rate of H 2 Sr elease relative to that observed for DTS-caged anilines. In the presence of cysteinea nd CA, we observed varying rates and quantities of H 2 Sr eleasef rom the reported arylbased DTS compoundsw ith 3-MePhDTS and 4-tBuPhDTS displaying the fastest and slowest rates of H 2 Sr elease, respectively ( Figure 3a).…”

“…General procedure for the synthesis of thiocarbamates:T his procedure has been modified from ap revious report. [33] In af lamedried round bottom flask under nitrogen, sodium hydride (1.25 equiv) and N,N-dimethylethanolamine were added to anhydrous toluene (20 mL). After stirring briefly until gas evolution ceased, the desired isothiocyanate (1.0 equiv) was added dropwise (if liquid) or in as ingle portion (if solid).…”

“…General procedure for the synthesis of dithiasuccinoyls:T his procedure has been modified from aprevious report. [33] To af lamedried round bottom flask under N 2 ,c hlorocarbonylsulfenyl chloride (1.0 equiv) was added to anhydrous DCM (20 mL). In as eparate vial, the desired thiocarbamate (1.0 equiv) was dissolved in anhydrous DCM (1 mL) and added dropwise to the reaction.…”

Use of Dithiasuccinoyl‐Caged Amines Enables COS/H2S Release Lacking Electrophilic Byproducts

“…With a small library of DTS‐based donors in hand, we next examined the effect of the amine payload on COS/H 2 S release using each donor (25 μ m ) in the presence of cysteine (500 μ m , 20 equiv) and CA (25 μg mL −1 ) at physiological pH (Figure ). We hypothesized that DTS‐caging of functionalized anilines would allow COS/H 2 S release rates to be tuned based on prior work aimed at solvent‐dependent linear free energy relationship investigations into the phosphine‐mediated sulfur extrusion from DTS . Additionally, we expected that the caging of alkyl amines would lead to stabilization of the COS‐releasing thiocarbamic acid intermediate and subsequently decrease the rate of H 2 S release relative to that observed for DTS‐caged anilines.…”

“…General procedure for the synthesis of thiocarbamates : This procedure has been modified from a previous report . In a flame‐dried round bottom flask under nitrogen, sodium hydride (1.25 equiv) and N , N ‐dimethylethanolamine were added to anhydrous toluene (20 mL).…”